Attention allocation during the observation of biological motion: an EEG study

The processing of observed biological motion that is the movement of biological organisms has an important role in animals’ vigilance and survival. For humans, it is also implicated in the development of social cognition and communication, with infants showing preferential attention towards motion from an early age. Further, adults can extract a broad range of social information from the biological motion of human figures represented by dots of light (point-light displays), that contain kinematic, structural and dynamic information. From this information, humans can identify individual actors, their sex, emotional state (angry, happy, and sad) and walking direction even when obfuscated by additional noise. The processing of biological motion draws on different cognitive systems such as working memory, selective attention and sensorimotor processing. Humans demonstrate an attentional bias towards human forms and biological motion, compared to other non-biological stimuli, and the observation of biological movement activates sensorimotor cortical regions. Previous research has used EEG to measure mu frequency (~ 8-13 Hz) changes and to infer the activation of sensorimotor regions during biological movement observation. This sensorimotor activation is thought to be an indication of online movement simulation. It has been demonstrated that top-down attentional processes modulate the engagement of sensorimotor simulation during movement observation. What remains unknown is whether biological motion exogenously captures spatial attention and, in turn, modulates sensorimotor simulation; the current study sought to explore this question.
In the current study, I used an attentional bias paradigm where movement and control point-light displays are presented laterally and simultaneously as irrelevant cues. Relatively decreased reaction times to subsequent targets that appear in the same location as a cue reflects preferential processing of that preceding cue. I simultaneously recorded EEG and calculated mu frequency changes at both central and occipital electrode locations. I find decreased reaction times and an increase in correct responses to targets that replace the scrambled point light display (PLD), which represents non-biological motion, compared to targets that replaced the coherent PLD representing biological movement. In addition, EEG analysis revealed a left hemisphere bias, with post hoc analysis revealing this bias is driven by the central electrodes; with a larger desynchronisation in the left central electrode compared to the right central electrode, whereas, occipital alpha was desynchronised symmetrically. Together, the behavioural and EEG findings suggest an inhibition of return (IOR) effect.